1. Field of the Invention
This invention relates to combustion systems having means for automatic, real-time control of the combustion process which can be applied with significant advantage to a wide range of furnaces, boilers and combustors. This invention also relates to a burner for said combustion system which, in addition to means for adjusting the firing rate and air/fuel ratio, also comprises means for adjusting flame size and shape and the degree of mixing of fuel and oxidant.
2. Description of Prior Art
For many years, efforts in the area of combustion have been focused on improving burner efficiency and lowering emissions from the combustion process. These efforts have provided significant advances in burner technology while increasing efficiency and lowering emissions. However, these effort have provided diminishing returns to combustion system operators. Currently, the greatest potential for furnace combustion improvement rests with taking a more global approach in which burners are considered as part of an interactive, real-time furnace control system. Such systems would be able to monitor, control, regulate, set or adjust the combustion process including flame characteristics and emissions over a wide turndown range and with fuel switching providing maximum thermal efficiency and minimum emissions production over substantially all furnace operating conditions, including transient operation.
Conventional combustion systems in use today comprise burners which are adjustable primarily with respect to firing rate and air/fuel ratio. As a result, these burners are tuned to a compromise setting so as to provide reasonable values of emissions and heat transfer over a wide range of firing rates. However, other than changes in flame characteristics resulting from changes in firing rate and/or oxidant/fuel ratio, these systems do not provide flame shape control or oxidant/fuel mixing control. In addition, burners used by conventional combustion systems are frequently exposed to high temperatures resulting in high maintenance and shortened service life. Accordingly, there is a need for a xe2x80x9csmartxe2x80x9d combustion system which can provide interactive and flexible control of the combustion process in furnaces and other combustion chambers, very effective heat transfer to a load with emissions control over high turndown ratios, with multiple fuels, and during both steady-state and transient operation.
Accordingly, it is one object of this invention to provide an interactive, real-time furnace control system which, in addition to providing control over firing rate and oxidant/fuel ratio, also provides flame shape control and oxidant/fuel mixing control.
It is another object of this invention to provide a flexible combustion system which provides very effective heat transfer to a load over high turndown ratios, with multiple fuels, and during both steady-state and transient operation.
It is yet another object of this invention to provide a combustion system with a burner providing controlled localized flame stoichiometry over a wide turndown range using multiple fuels.
These and other objects of this invention are addressed by a combustion system comprising a burner body having a primary combustion oxidant (first fluid) inlet end forming at least one primary combustion oxidant (first fluid) inlet and a combustion oxidant (first fluid) outlet end forming at least one combustion oxidant (first fluid) outlet, a fuel (second fluid) inlet distal from the combustion oxidant (first fluid) outlet and at least one fuel (second fluid) outlet proximate the combustion oxidant (first fluid) outlet, and internal adjustment means for adjusting the flow cross-sectional area for a first fluid, typically oxidant, and/or a second fluid, typically fuel, disposed within the burner body. However, it will be apparent to those skilled in the art that the first fluid may be a fuel and the second fluid an oxidant. The combustion system further comprises interactive flame sensing and control means for providing interactive, real-time control over the combustion process, including control over flame size and shape and air/fuel mixing at constant fuel input.